Ten-Year Analysis of the Dynamics of the Goulbi’N Maradi Alluvial Aquifer from 2013 to 2022 in Niger

In the Maradi region, the alluvial aquifer of the Goulbi'N Maradi rests on the aquifers of the Continental Hamadien. It represents an essential reserve for irrigation and drinking water supply. However, due to its high demand and the excessive use of chemical fertilizers and pesticides in irrigation, a ten-year analysis of the dynamics of this alluvial aquifer has proven necessary. Hence, this study, based on hydrodynamic and hydrochemical approaches, aims to improve knowledge of the dynamics of the alluvial aquifer from 2015 to 2023. The novelty of this study lies in its comprehensive coverage of the entire Goulbi N’Maradi valley in Niger, employing a multidimensional approach. The data used were composed of water samples taken from forty-five structures, piezometric monitoring sheets, and digital terrain models. The results reveal that the Goulbi'N Maradi aquifer exhibits continuous piezometry, characterized by a general flow pattern from south to northwest and a relatively strong hydraulic gradient in the southern part, indicating recharge from recent infiltration of rain and floodwaters. The water balances calculated at a monthly time step showed that only July and August had surpluses, with average infiltrations of 25.4 mm and 23.9 mm for 2018 and an RFU of 50 mm. For 2021, the average infiltrations were 30.8 mm and 6.6 mm, respectively, for August and September, and for the same RFU. The water conductivity values between 115 and 800 µS·cm⁻¹. The hydrogen potential varied between 5 and 7 pH units, giving the water an acidic character that makes it corrosive to equipment.